This invention relates to outboard jet drive marine propulsion systems. The present invention relates to an outboard jet drive for a boat and especially to an outboard jet drive having an engine and jet drive mounted in a housing, which is removably attached to a boat hull.
There have been several proposed types of outboard set drives for watercraft but most are similar to an outboard motor in which the outboard motor propeller and lower unit have been replaced with a jet drive. The jet drive includes a jet pump in the lower unit that operates to provide propulsion force for a watercraft. There are advantages in employing jet pumps for propulsion units as opposed to propellers. The jet drive permits operation in shallower water, also the propeller is shrouded, and there is less likelihood of injury. There has been a variety of proposed constructions for outboard jet drives for positioning the jet pump in different positions relative to the hull transom and bottom of the transom but in a typical jet drive, the engine and jet drive are located directly in the hull with an opening in the bottom of the hull for capturing water passing under the hull and then utilizing the jet pumps to thrust the water out the rear of the hull to propel the boat. Outboard jet drive units are made similar to typical outboard motors with a motor driving a drive unit, which operates a jet drive unit.
Generally, the engine package includes an internal combustion engine mounted in a thin fiberglass hull. The base plate of the hull includes a water inlet scoop for feeding water to the pump and an exhaust port for exhausting the water. The pumps high-pressure water outlet is pointed in the aft direction above the water line to propel the craft by the reaction force resulting from the high velocity water jet. In the F. C. Clark U.S. Pat. No. 3,055,175, a marine propulsion unit takes a conventional outboard motor and replaces the prop unit with a marine jet motor using a pump to issue a jet of water to propel a boat. The Parker U.S. Pat. No. 5,356,319, is for a boat with a removably inboard jet propulsion unit in which the integral jet power unit is encased in a waterproof housing and positioned in a well located in the hull and is mounted to be removed from the hull.
Many of the shortcomings of the prior art were overcome by Applicant's U.S. Pat. No. 6,398,600 in which an outboard jet propulsion unit is detachably mounted to a boat so that the main fuel tank and controls are mounted within the hull of a boat while the outboard jet drive unit is mounted away from the boat in a housing with an engine and is removably attached to the transom of the boat. The fuel tank and controls are connected between the hull and outboard drive through quick disconnect couplings. The housing is shaped to support an engine on a platform directly over the jet drive unit for actuating the jet drive unit through a clutch mechanism with the engine and jet drive positioned parallel to each other.
The outboard jet unit as designed by Applicant was satisfactory, however, it did not fully realize the efficiencies of jet propulsion. Accordingly, an outboard jet propulsion unit which overcomes the deficiencies of the prior art is desired.